The present invention pertains generally to machine elements and mechanisms, and more particularly to shaft alignment devices for pumps.
Various types of pumps are used for a wide range of applications. Many applications of pumps require generation of extremely high pressures to achieve a desired result. For example, mud pumps used in drilling processes are required to produce relatively large forces on the order of 4,000 lbs. per square foot to pump drilling mud a considerable vertical distance during the drilling procedure. As a result of the high pressures produced in the mud pump, considerable friction is generated as a result of the close tolerances in the reciprocating pump mechanism. These close tolerances require extremely accurate alignment of the cylinder and piston to reduce wear and increase the operating lifetime of the system. Mud pump cylinders have been designed with replaceable liners to reduce maintenance cost. Typical steel cylinder liners have an operating lifetime of approximately 1,000 hours. Additionally, replaceable seal mechanisms mounted on the piston have been designed to further reduce "down-time" and maintenance cost as disclosed in U.S. Pat. No. 4,380,951, the disclosure of which is incorporated herein by reference.
Ceramic cylinder liners, which have superior abrasion and corrosion resistance in comparison to conventional metal cylinder liners, have been developed. Such ceramic cylinder liners have expected lifetimes on the order of 5,000 hours. However, it has been found in operation that slight misalignment of the reciprocating shaft which drives the piston in the piston cylinder can cause excessive abrasion of the ceramic cylinder liner resulting in a greatly reduced operating lifetime. Hence, to employ the advantages of the ceramic cylinder liners it is necessary to very accurately align the reciprocating shaft with the cylinder. To date, it has been found to be extremely difficult, if not impossible, to align the reciprocating shaft with sufficient accuracy to take advantage of the superior qualities of the ceramic cylinder liners.